The present invention relates to testing of electrical circuits, and more specifically to testing of matched impedance test points on a circuit board by a time domain reflectometer (TDR) through an x-y prober.
Testing match impedance test points on a circuit board requires contacting the test points by test probes and analyzing the test signals with a time domain reflectometer. Previous TDR technology consisted of separate hand held probes consisting of a signal probe and a ground probe which were manually operated to contact the desired test locations. When multiple test locations exist for testing, manually testing each site is an inefficient and time consuming task. Consequently, more automated TDR configurations were developed consisting of an x-y prober wherein only one of the prober heads was used and was modified such that the signal wire and the ground shield of the TDR cable extended to the tip of one of the heads of the x-y prober. This single head was designed to be adjustable and rotatable for different test pad spacings. Incorporating a rotatable and adjustable tip on a single prober head is a very expensive and complicated device for testing matched impedance test points. Consequently, a need exists for an automated TDR tester capable of testing matched impedance test points that addresses the problems of the prior art and is easy and inexpensive to manufacture.